First, though, he wants to help "young, progressive Democrats" get elected -- maybe even to the Senate -- in his home state of Texas. Only after November will the 43-year-old Latino, whose twin brother, Joaquin, is in Congress, decide on his political future.

The former San Antonio mayor and Housing and Urban Development secretary under President Barack Obama launched the Opportunity First PAC as a vehicle for his political activity. He is set to make his first trip to an early voting state on February 16, when he'll be in Manchester to speak to New Hampshire Young Democrats.

CNN caught up with Castro after he spoke at an event at American University in Washington on Thursday. Here's what he said:

On running for President in 2020:

"Yeah, I'm interested, but whether or not I end up doing it -- I'll decide that later."

When will he decide?

"I have not decided to run. I'm going to take these next few months of the 2018 cycle helping young, progressive Democrats running across the country get elected. ... And then after that, after the November election, I'll make a decision by the end of 2018 about my own future. But during these next few months, I'm going to have a lot of chance to get across the country and listen to what folks are saying and get a sense of what people are thinking."

On visits to states like New Hampshire:

"Part of making a decision will be understanding those states better, spending time there."

How he'll prepare for his 2020 decision:

"Everybody's focus right now seems to be on 2018 for very good reason, and my focus is on 2018. But anybody who's thinking about running in 2020 is also, I would imagine, at least going through what that kind of race looks like. ... And what happens this November will probably impact the field that you see in 2020, too. Those two things are related."

His 2018 plans:

"I'm going to focus the vast majority of my attention on supporting great candidates all across Texas and across the United States. ... We've started to get requests at Opportunity First from people throughout the United States. My number one priority is doing what we can to build a great bench of young, progressive Democrats."

Is Texas winnable for Democrats?

"Texas had the highest jump toward the Democrats in the 2016 election, toward Secretary Clinton. I expect that in the Texas House of Representatives, Democrats will pick up perhaps 10 seats, maybe a state Senate seat or two, and that (the Democratic Senate candidate, Rep.) Beto O'Rourke runs right now a decent shot at beating Ted Cruz, which would be earth-shattering down there in Texas...

"It's the same abandonment of Trump by people in the suburbs that you saw in Northern Virginia (and Alabama). ... That's happening in the suburbs of Dallas, Houston, Austin, San Antonio. So it's not just sort of the two-dimensional demographic question we think about in terms of the Latino community. It's also that you have folks in these big-city suburbs that used to be moderate Republicans that, more and more in Texas, have become independents or Democrats. And Trump has done that, and Cruz is having trouble with them right now."